Perforation of laundry machine drum

ABSTRACT

A laundry machine drum has a sheet material skin including an arrangement of a plurality of perforations therethrough. Each of one or more of the perforations includes a shear cut in the sheet material. The sheet is deformed in the region of the shear cut such that the edge of the sheet material of one side of the shear cut is offset from the edge of the sheet material of the other side of the shear cut over at least some of the length of the shear cut. An opening is formed between the offset edges. The apparent area of the opening is greater when viewed from at least one direction substantially parallel to the general plane of the drum skin in the region of the perforation than when viewed from a direction substantially perpendicular to the general plane of the drum skin in the region of the perforation.

BACKGROUND TO THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to laundry machine drums and inparticular to the form of perforations in the laundry machine drum skinand to methods of forming same.

[0003] 2. Summary of the Prior Art

[0004] In laundry machines, of both horizontal and vertical axisvarieties, it is well known to provide a drum having a metal, forexample stainless steel, drum skin. In general this drum skin isprovided with an arrangement of a plurality of openings therethrough.These openings are for example plain holes through the drum skin whichmay be formed by punching or by lancing from the inside surface of theskin.

[0005] In a washing or rinsing operation wash liquids may pass throughthe drum skin in one or other direction. In a dehydration operation washliquids are extracted from a saturated clothes load retained within thedrum by centrifugal force when the drum is spun at high speeds.

[0006] It is known in the prior art that burrs on the outermost edge ofthe sheet metal at the holes are dangerous to the fingertips of a userof a laundry machine and/or to laundry. The burrs may catch laundryfibres which may pass outwardly through the holes and become caught.

[0007] Furthermore it has been found that there is a limitation onmaximum drum spinning speeds that can be safely used where a plain holeperforation is adopted. Where the spinning speed reaches above a certainlevel and the centrifugal forces become too great, either the laundryfabrics are drawn outwardly through the plain holes or the fabricspanning the plain hole tears outwardly at its centre under the forcesexerted. If the laundry extrudes outwardly through He holes it may betom when removing the laundry from the surface of the drum even thoughburrs may not be present at the outer edges of the plain holes.

SUMMARY OF THE INVENTION

[0008] It is accordingly an object of the invention to provide a laundrydrum for a washing machine incorporating perforations which will atleast go some way towards overcoming the above disadvantages and/or toprovide a method of forming such perforations.

[0009] In a first aspect the invention consists in a laundry machinedrum having a sheet material skin including an arrangement of aplurality of perforations therethrough, each of one or more of saidperforations including:

[0010] a shear cut in said sheet material, the sheet being deformed inthe region of said shear cut such that the edge of the sheet material ofone side of said shear cut is offset from the edge of the sheet materialof the other side of said shear cut over at least some of the length ofsaid shear cut such that an opening is formed between said offset edgesand the apparent area of said opening is greater when viewed from atleast one direction substantially parallel to the general plane of saiddrum skin in the region of said perforation than when viewed from adirection substantially perpendicular to tie general plane of said drumskin in said region of said perforation.

[0011] In a further aspect the invention consists in a method of forminga perforation in a laundry machine comprising operating on a sheetmaterial with a punch and corresponding die,

[0012] said punch having a leading face, and a shearing edge definingone edge of said leading face,

[0013] said die having a leading face and a complementary shearing edgeto said punch shearing edge,

[0014] said leading faces and shearing edges of said punch and said dieformed such that movement of said punch in an advance direction relativeto said die causes said shearing edge of said punch to overlap with saidshearing edge of said die at at least the middle of said shearing edges,and to overlap progressively less away from the middle of said shearingedges, to produce a sheared cut in a material placed there between whichprogressively reduces in displacement from its middle to its ends.

[0015] In still further aspect the invention may broadly be said toconsist in a laundry machine drum having a sheet material skin includingan arrangement of a plurality of perforations therethrough, each of oneor more of said perforations being formed in accordance with a method asset forth above.

[0016] In a still farther aspect the invention may broadly be said toconsist in a laundry machine drum having a sheet material skin includingan arrangement of a plurality of openings therethrough, at least onesaid opening having a form such that the apparent area of said openingis greater when viewed from at least one direction substantiallyparallel to the general plane of said drum skin in the region of saidperforation than when viewed from a direction substantiallyperpendicular to the general plane of said drum skin in said region ofsaid perforation.

[0017] To those skilled in the art to which the invention relates, manychanges in construction and widely differing embodiments andapplications of the invention will suggest themselves without departingfrom the scope of the invention as defined in the appended claims, Thedisclosures and the descriptions herein are purely illustrative and arenot intended to be in any sense limiting.

BRIEF DESCRIPTION OF TEE DRAWINGS

[0018]FIG. 1 is a perspective view of a small portion of a drum skinincluding a perforation according to a preferred embodiment of thepresent invention when viewed from inside the drum.

[0019]FIG. 2 is a perspective view of a small portion of a drum skinincluding a perforation according to a preferred embodiment of thepresent invention when viewed from outside the drum.

[0020]FIG. 3 is an end elevation of a punch for use in forming a drumperforation as in FIGS. 1 and 2.

[0021]FIG. 4 is a cross sectional side elevation of a punch and dieoperating on a sheet material in forming a perforation according toFIGS. 1 and 2, said side elevation taken through plane AA in FIG. 3.

[0022]FIG. 5 is a cross sectional side elevation of a punch and dieoperating on a sheet material in forming a perforation according toFIGS. 1 and 2, said side elevation taken through plane BB in FIG. 3.

[0023]FIG. 6 is a cross sectional side elevation of a drum skin from ashallow angle with the cross section taken across the perforationaccording to the preferred form of the present invention.

[0024]FIG. 7 is a cross sectional side elevation of a drum skin from ashallow angle with the cross section taken across the perforationaccording to the preferred form of the present invention from adirection perpendicular to the direction of FIG. 6.

DETAILED DESCRIPTION

[0025] The present invention relates to a new form of perforation forthe skin of a laundry machine drum. This drum may be of a washingmachine of horizontal or vertical axis or could for example be of aclothes dryer. Typically the drum skin will have a geometrical array orpattern of openings or perforations over the area thereof. All of theopenings may be of the form according to the present invention oralternatively only a proportion may have such form. For example it isconsidered that perforations or openings in the drum end may remainplain holes, the surfaces of the drum ends for example being at leastsubstantially parallel to the centrifugal force generated in adehydrational spin operation.

[0026] Referring then to the form of perforation according to thepreferred embodiment of the present invention this is illustrated inFIGS. 1, 2, 6 and 7.

[0027] Referring to FIG. 1 a section of drum skin 1 is shown. A circularsemi spherical depression 2 is apparent on the inner surface of the drumskin 1. The semi spherical depression 2 accordingly corresponds with adimple or dome shape 3 apparent on the outer surface in FIG. 2. Thedepression 2 is not semi spherical to its full depth. At a partial depththereof a pair of flat surfaces 4 intrude the semi spherical depressionand are substantially parallel in orientation with the general plane ofthe drum skin 1 in the region of the perforation. These surfaces end atedges 5 Edges 5 are parallel and spaced apart. For reasons which willbecome apparent when the forming method is described the edges 5 may bereferred to as shear edges. A bridge 6 of material continues thehemispherical shape of the hemispherical depression 2. Bridge 6 isbounded at the sides thereof by shear edges 7. The shapes thus definedleave a pair of openings 8, one at each side of the bridge 6, each ofwhose perimeter is defined by a shear edge 7 of the bridge 6 and a shearedge 5 of a flat 4.

[0028] It will be readily appreciated that variations on the proposedperforations are possible, and on the proposed tools for implementingsame. For example it will be appreciated that it is not requisite thateither or both of the shear cuts be a straight cut and that these cutscould instead be curved in the plane of the sheet. Thus for examplewhere two such shear cuts are present and they are referred to as beingparallel his means in a broad or overall context and is not to be readas being strictly limiting.

[0029] As will be apparent from FIGS. 6 and 7 when viewed from adirection which is at least substantially perpendicular to the generalplane of the sheet in the region of the perforation, for example adirection as indicated by arrow 9, the openings 8 have little or noapparent area. However when viewed from at least one direction, forexample as indicated by arrow 10 substantially parallel with the generalplane of the sheet in the region of the perforation the entire ormaximum area of the openings 8 is visible. Such as the view of theopenings 8 depicted more or less in FIG. 7.

[0030] The forming process for a perforation in accordance with thepresent invention is illustrated with particular reference to FIGS. 3 to5. In these Figures forming of the perforation according to thepreferred embodiment of the present invention is depicted using a punchtool 11 and a cooperating die tool 12. An end elevation of he punch tool11 is shown in FIG. 3. The punch tool 11 has a semi spherical endsurface 13. The semi spherical end surface 13 spans the perimeter regionof the punch tool end. It also spans a bridging region 14 definedbetween a pair of cutting or leading edges 15. Bridging portion 14 ofsemi spherical face 13 will be a leading face of the punch tool 11 inuse,

[0031] A pair of rebates or notches are formed in the semi sphericalface 13, resulting in a pair of semi circular flat faces 16 which in useform trailing faces of the punch tool. 1. The semi circular trailingfaces 16 in use form the flat portions 4 of the formed perforation. Theleading face 14 forms the bridge 6 of the perforation. A shear wall 17substantially parallel with the intended direction of travel of thepunch tool 11 and substantially perpendicular to both the leading face14 and the semi circular faces 16, extends between the semi circularfaces 16 and the leading face 14, meeting the leading face 14 at shearedges 15. It will be readily appreciated that these shear walls arethemselves semi circular in form.

[0032] Referring then to FIGS. 4 and 5 the punch tool 11 cooperates inuse with a die 12. A sheet 1 to be formed is clamped between a peripheryface 18 of the die 12 and a clamping face 19 of an annular clampingblock 20 through which the punch tool 11 passes in use. The clampingbetween the clamping tool 20 and the die 12 secures the sheet 1 inposition.

[0033] The die 12 has a circular rebate 21 to a depth whichsubstantially complements the depth of the annular semi sphericalperiphery region of surface 13 of the punch tool 11. A channel 22 isfurther formed spanning across this circular rebate 21 and the basethereof The channel 22 is of substantially the same width, althoughslightly greater to tolerance, as the leading face 14 of the punch tool11. It is of cooperating form, such that the edges 24 formed between theside walls 23 of the channel 22 and the bottom face 25 of the circularrebate 21 cooperate with the shear edges 15 of the punch tool 11 in ashearing action to shear a sheet 1 of material upon movement of thepunch tool 11 fully into the die cavity until the trailing faces 16 ofthe tool and the bottom faces or anvil faces 25 of the circular rebate21 come together with the flat faces 4 of the sheet 1 therebetween. Thisshearing action between the shearing edge 24 of the die 12 and theshearing edge 15 of the punch 11 and subsequent deformation of thebridge portion 6 of the sheet 1 beyond the position of the flat faces 4forms openings 8.

[0034] A number of variations on the invention will be apparent. Forexample the perforation may incorporate only a single shear cut ratherthan a pair of opposing myriad shear cuts. This would however have thedisadvantage of unbalanced side loading on the punch tool 11 in thepunching process. In addition it will be appreciated that thehemispherical depression is not a necessary part of the perforation, andthat an arching bridge or trapezoidal bridge might be pushed from theplane of the sheet without deforming the sheet in the general area ofsuch a bridge.

[0035] It will also be appreciated that perforations maybe formed by analternative process which have the same essential characteristic ofapparent area from a direction perpendicular to the sheet being lessthan the apparent area from a direction parallel to the sheet. Forexample such a perforation might possibly be formed by lancing a holethrough the drum skin and subsequently rotating the axis of the lance toa direction substantially parallel with the skin prior to withdrawal.Adaptations of such a process to further incorporate a die or similarcooperating surface on the opposed side of the sheet might also beenvisaged. While this is not considered a preferred method of forming, aperforation thus formed does not depart from the scope of the inventionin its broadest sense.

1. A laundry machine drum having a sheet material skin including anarrangement of a plurality of perforations therethrough, each of one ormore of said perforations including: a shear cut in said sheet material,the sheet being deformed in the region of said shear cut such that theedge of the sheet material of one side of said shear cut is offset fromthe edge of the sheet material of the other side of said shear cut overat least some of the length of said shear cut such that an opening isformed between said offset edges and the apparent area of said openingis greater when viewed from at least one direction substantiallyparallel to the general plane of said drum skin in the region of saidperforation than when viewed from a direction substantiallyperpendicular to the general plane of said drum skin in said region ofsaid perforation.
 2. A laundry machine drum as claimed in claim 1wherein said deformed sheet material the material of one said side ofsaid shear cut is displaced outward from the material of the other sideof said shear cut relative to the intended spin axis of said drum, butthe planar orientation of said regions immediately adjacent the edges ofsaid regions at said shear cut are parallel to one another.
 3. A laundrymachine drum as claimed in claim 2 wherein said drum includes at leastone group of two or more said perforations, said group defined by theirproximity to one another, said openings of said group of perforationsacing a common centre.
 4. A laundry machine drum as claimed in claim 1wherein said drum includes at least one group of two or more saidperforations, said group defined by their proximity to one another, saidopenings of said group of perforations facing a common centre.
 5. Alaundry machine drum as claimed in any one of claims 1 to claim 3wherein at least one said drum perforation is located within a dish inthe drum skin extending outwardly relative to the drum spin axis.
 6. Alaundry machine dram as claimed in claim 4 wherein said group of drumperforations is located within a dish in the drum skin extendingoutwardly relative to the drum spin axis.
 7. A laundry machine drum asclaimed in claim 6 wherein said dish includes two said perforationsopposingly oriented to one another such that the shear cuts thereof areparallel and a bridge of material is defined by said parallel cuts.
 8. Alaundry machine dram as claimed in claim 7 wherein said bridge ofmaterial is spaced outwardly further than the remaining material of saiddish or dimple relative to said dram spin axis.
 9. A laundry machinedrum as claimed in claim 7 wherein said bridge of material is spacedinwardly further than the remaining material of said dish or dimplerelative to said drum spin axis.
 10. A method of forming a perforationin a laundry machine comprising operating on a sheet material with apunch and corresponding die, said punch having a leading face, and ashearing edge defining one edge of said leading face, said die having aleading face and a complementary shearing edge to said punch shearingedge, said leading faces and shearing edges of said punch and said dieformed such that movement of said punch in an advance direction relativeto said die causes said shearing edge of said punch to overlap with saidshearing edge of said die at at least the middle of said shearing edges,and to overlap progressively less away from the middle of said shearingedges, to produce a sheared cut in a material placed there between whichprogressively reduces in displacement from its middle to its ends.
 11. Amethod as claimed in claim 10 wherein said punch includes at least onefurther shear edge matching said first said shear edge but spaced aparttherefrom, said shear edges of said punch facing a common centre, suchthat said leading face is defined by said shear edges, and said dieincludes at least one further die shear edge matching said first dieshear edge but spaced apart therefrom, said die shear edges facing acommon centre, such that said leading face of said die is defined bysaid die shear edges, said die shear edges matching and aligned withsaid punch shear edges, such that in said operation said punch and saiddie create a plurality of peripherally spaced shear cuts.
 12. A methodas claimed in claim 11 wherein said orientation of said die shear edgesand said punch shear edges is such that said openings of said shear cutsall face toward said common centre when viewed from one side of saidsheet.
 13. A method as claimed in claim 12 wherein said openings of saidshear cuts all face toward said common centre when viewed from adjacentsaid sheet on the intended inside of said drum.
 14. A method as claimedin claim 10 wherein said punch has a trailing face parallel in one axisto said leading face, and a shear wall perpendicular in said axis tosaid leading and said trailing faces and connecting therebetween, saidperpendicular shear wall tapering to ends thereof such that at said endsthereof said leading face and said trailing face meet, and said die hasa complementary anvil face for at least said trailing face of saidpunch, an edge of said anvil ice being aligned to cooperate with saidshear edge of said die to shear a sheet material by relative movementtherebetween.
 15. A method as claimed in claim 14 wherein said dieincludes a second shear wall parallel to, opposed to and matching saidfist said shear wall but spaced apart therefrom such that said leadingface is defined along two parallel edges thereof by said two shearwalls, a second said trailing face extending at the base of said secondshear wall, aligned with the first said trailing face, and said dieincludes a second said anvil face complementary to said second trailingface and having a shear edge thereon parallel to said shear edge on saidfirst anvil face and opposed thereto across a gap, the width of said gapmatching the width of said leading face of said tool but for a toolclearance.
 16. A laundry machine drum having a sheet material skinincluding an arrangement of a plurality of perforations therethrough atleast one said perforations being formed according to a method asclaimed in any one of claims 10 to
 15. 17. A laundry machine drum havinga sheet material skin including an arrangement of a plurality ofopenings therethrough, at least one said openings having a form suchthat the apparent area of said opening is greater when viewed from atleast one direction substantially parallel to the general plane of saiddrum skin in the region of said perforation than when viewed from adirection substantially perpendicular to the general plane of said drumskin in said region of said perforation.